One of the most common problems with bulk solids such as coal, sugar, flour and other various chemicals is arching or bridging at the outlet of a converging hopper. The usual solutions for eliminating bridges include enlarging the outlet beyond the critical size for bridging, and using physical agitation such as air blasters, vibrators, air lances and poke bars to dislodge the solids. While physical agitation works to some extent when arching occurs only after time at rest, the only effective way presently to handle a bulk solid that arches instantly when placed in a hopper is to enlarge the outlet size. This increases the size and cost of the feed device required below the outlet.